Tire sensor localization utilizing speed corrected frequency

ABSTRACT

A method of localizing the location of a received signal from a tire pressure sensor includes sending an AM identification signal. The AM signal is adjusted for speed such that the frequency of the signal equals a constant multiplied by the speed of the vehicle. Each of the tire locations on a vehicle have an expected sequence of black-out points in the signal received by a receiver at any point on the vehicle. That is, given a particular vehicle design, the AM signal described above would be received at a receiver with an expected sequence of received peaks and black-out points. Since the frequency of the signal is adjusted for speed, the received signal will accurately allow the location of black-out points to be utilized to identify the tire location for a particular signal.

[0001] The present invention claims priority to U.S. Provisional PatentApplication Serial No. 60/394,180 filed on Jul. 3, 2002.

BACKGROUND OF THE INVENTION

[0002] This invention relates to the use of a signal being transmittedfrom tire pressure sensors wherein a signal is adjusted to have afrequency corrected for the speed of the vehicle. A control receives thesignal and identifies characteristics in the signal to identify whichtire has sent the signal.

[0003] Modem vehicles are being provided with more and more electronicdiagnostic and sensing systems. In particular, tire pressure sensors arenow incorporated into most modem vehicles. The tire pressure sensorstypically send a wireless signal to a control. The signal will typicallyinclude a code, such that the control can identify to which tire theparticular signal relates.

[0004] Such tire pressure monitoring systems require some way ofinitially identifying the code for each sensor and its associated tirewith a control. Thus, means for “localization” are incorporated intotire pressure monitoring systems.

[0005] One proposed system looks at characteristics in the signal thatwould be distinct for each of the tire based sensor transmitters. As anexample, due to the relative location of the receiver and the controland each of the sensors on each of the tires, there would be distinct“black spots” within the signal at which the receiver would not receivea portion of the signal. The pattern of black spots could thus be ofvalue in identifying the location of the particular sensor sending theparticular signal. A receiver could be programmed to expect a particularseries of black spots at particular times, and identify which tire isreporting based upon those black spots. However, the speed of thevehicle would affect the expected timing of the black spots within thesignal. Thus, the prior art discussed above is not a practical way ofidentifying the location of a sensor sending a particular transmission.

SUMMARY OF THE INVENTION

[0006] In a disclosed embodiment of this invention, a signal istransmitted from sensors associated with each of the tires when acontrol is in a “learn” mode. This signal has a frequency that isadjusted to be corrected for vehicle speed. The frequency is equal tosome constant multiplied by the speed of the vehicle such that thefrequency of the transmission of the signal is relatively constant. Inthis manner, the receiver for a control can receive the signal andcompare it to expected “black” spots for a signal from each of thetires. The receiver thus identifies the source of each signal.

[0007] In a most preferred embodiment, the signal is amplitude modulatedand the receiver includes an amplitude peak detector for receiving thesignal. The signal is preferably imposed upon the transmission from thetire pressure sensors for at least one, and preferably several,rotations of each tire every time the vehicle has stopped for at least apre-determined period of time.

[0008] These and other features of this invention can be best understoodfrom the following specification and drawings, the following of which isa brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a schematic view of the system incorporating the presentinvention.

[0010]FIG. 2 is a flowchart.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0011] A vehicle 20 is illustrated in FIG. 1 having four tires 22, 24,26 and 28. The tires have tire pressure monitoring sensors andtransmitters 23, 25, 27 and 29. Each of these sensors/transmitterstransmit signals S1, S2, S3 and S4.

[0012] All of the signals S1-S4 are received by a common receiver andcontrol 30. Control 30 must be capable of receiving the signals S1-S4and looking at embedded codes unique to the sensors 23, 25, 27 and 29.Each code is stored at the control such that when subsequent signals arereceived, the control can identify which tire is associated with aparticular signal.

[0013] As also shown in FIG. 1, the signals S1-S4 have a unique sequenceof zeros and “black spots” at any one speed. The unique sequence isbased upon the geometry of the vehicle, the relative location of thetires and the receiver, etc. For a particular vehicle design, a controlcan be programmed to expect a particular sequence for each of the fourtire locations. Thus, the control 30 could be programmed with thesequence such as shown in the box in FIG. 1. Of course, the illustratedsequences are simply examples made for an understanding of thisinvention. Actual sequences would be determined experimentally or byprediction once a particular vehicle design has been finalized.

[0014] The present invention makes a practical application of thesesequences to identify the location of each of the sensors by correctingthe frequency of the transmission for changing vehicle speeds. Many ofthe known pressure sensors in the tires also contain a speed sensor todetermine vehicle speed. Essentially, location signals are sent by thesensors 23, 25, 27, and 29 as an AM signal having a frequencyproportional to the speed of the vehicle. Thus, the frequency is equalto some constant times the speed of the vehicle. As the speed increases,the frequency of transmission increases. This correction for speedshould ensure that the sequence will be generally the same for each ofthe tires, regardless of changes in vehicle speed.

[0015] Most preferably, the AM signal being sent at the speed dependentfrequency need only be sent for at least one or perhaps a few rotationsof each tire after the vehicle has been stopped for a predeterminedperiod of time. Each time the vehicle has stopped for a predeterminedperiod of time, on the order of at least several minutes, it isdesirable to relearn the codes. This anticipates that during thestoppage of the vehicle, the tires may have been rotated, replaced, etc.

[0016] After the termination of this identification signal, thetransmitter would return to its normal transmission of the tire pressuresignal information. Typically, the tire pressure information is sentperiodically, and includes an identifier code along with pressureinformation. The control 30 will have stored the identifier code that isalso part of the identification signal.

[0017] Although a preferred embodiment of this invention has beendisclosed, a worker of ordinary skill in the art would recognize thatcertain modifications would come within the scope of this invention. Forthat reason, the following claims should be studied to determine thetrue scope and content of this invention.

What is claimed is:
 1. A tire pressure monitoring system comprising: aplurality of tire pressure sensor and transmitter; a receiver andcontrol for receiving signals transmitted by each of said tire pressuresensor/transmitters; said tire pressure sensor/transmitters includingthe ability to send an identification signal; and a control associatewith said sensor/transmitters monitoring vehicle speed, and adjustingthe frequency of transmission of said identification signal to bedependent upon said detected vehicle speed.
 2. A system as set forth inclaim 1, wherein said identification signal is an AM signal which has afrequency equal to some constant multiplied by said detected speed.
 3. Asystem as set forth in claim 1, wherein said identification signal isonly sent when the vehicle has been stopped for a predetermined periodof time.
 4. A system as set forth in claim 3, wherein saididentification signal is only transmitted for a predetermined number ofrevolutions of the tire after beginning transmission.
 5. A system as setforth in claim 1, wherein said identification signal includes anidentifying code, and said tire pressure sensor/transmitters furtherperiodically sending tire pressure signals also including saididentifying code.
 6. A method of localizing a received signal from avehicle comprising the steps: (1) identifying an expected sequence ofblack-outs in a received signal from each of four tire locations on avehicle, and storing said expected sequence in a control; (2) operatinga vehicle and transmitting identification signals from each of said atleast four tire locations on a vehicle, and receiving signals from eachof said four tire locations, and identifying the sequence of black-outsin each of said four identified signals, said transmitting of saididentification signal including the adjustment of the frequency of saidtransmission of said identification signal being based upon a detectedvehicle speed; and (3) comparing said sequence of black-out points insaid received signals to said expected sequence of black-outs, andidentifying a tire location for any of said sequence of said receivedsignals which matches an expected sequence of said signals.
 7. A methodas set forth in claim 6, wherein said transmitted signals furtherinclude an identifier code, and said identifier code being stored insaid control, said subsequent signals being identified for a particulartire location without any need for the comparison of Step (3).
 8. Amethod as set forth in claim 6, wherein said adjustment of saidfrequency of transmission of said identification signal including makingsaid frequency proportional to vehicle speed such that increasingvehicle speed results in increasing frequency of transmission of saididentification signal.